The association of immature cellular respiration with susceptibility to hyperthermia-induced seizures will be studied in the rat pup. The protocols are designed to test the potential use of hyperthermia-induced seizures in the rat as a model for febrile convulsions in the young child. An age-dependent increase in threshold for these seizures will be studied. In analogy with the proposed causative role of early febrile seizures in the genesis of temporal lobe epilepsy, the effects of early hyperthermia-induced seizures on the morphology and electrophysiology of the hippocampus will be studied. The efficacy of various anticonvulsants will be measured in this seizure model. Cellular respiration will be measured in slices from the brains of immature and adult animals under physiologic conditions and under conditions of acidosis, hyperkalemia, and elevated temperature. These results will be compared to studies of such properties in the developing brain in situ and to properties of separated or cultured cells and mitochondria isolated from the developing brain. These studies are a continuation of the PI's work of the maturation of cerebral energy metabolism at the subcellular and cellular levels. Age-dependent changes and changes secondary to hyperthermia-induced seizures in these cellular respiratory properties will be compared to changes in seizure threshold with maturation and with previous seizures. Changes in cellular respiration which are associated with changes in seizure threshold under both conditions will be considered of probable importance in the genesis of hyperthermia-induced seizures in th rat pup and, by analogy, to the genesis of febrile seizures in the child.